The present invention relates to the field of integrated circuits, and more particularly to a semiconductor device, and method of fabricating the semiconductor device including an image sensor.
An image sensor is able to receive information of an optical image and convert the information into an electric signal. An image sensor may be based on the principle of its implementation into a charge coupled device (commonly known as a CCD image sensor) and a CMOS image sensor, where the CMOS image sensor is based on complementary metal-oxide semiconductor (CMOS) manufacturing technology. Because a CMOS image sensor is fabricated using conventional CMOS manufacturing processes, it can be integrated with other peripheral circuits so that the CMOS image sensor has a broad range of applications.
According to different positions of the light receiving component, CMOS image sensors can be divided into front-illuminated CMOS image sensors and back-illuminated CMOS image sensors. In a front-illuminated CMOS image sensor, the photodiode is disposed behind the transistor circuit so that an amount of incident light is blocked by the transistor circuit, reducing the quantum conversion efficiency. Back-illuminated CMOS image sensors have advantages over front-illuminated CMOS image sensors in that the internal structure is reversed so that light enters the back side of the CMOS image sensor can reach directly the photodiode. Light is affected by the structure between the microlens and the photodiode and the thickness of the structure so that the effectiveness of the received light can be improved.
Conventional front-illuminated CMOS image sensors and back-illuminated image sensors have the photodiode and the transistor circuit integrated on the same chip, and each photodiode together with 1 to 5 transistors form a pixel as the basic unit of the image forming unit. However, the transistors hinder light absorption of the photodiode so that light receiving efficiency is reduced, leading to reduced quantum conversion efficiency of the photodiode.
In view of the foregoing, there is a need for a novel semiconductor device and method for manufacturing the semiconductor device that can overcome the deficiencies of the prior art.